Self-assembling polymers—V

ABSTRACT

Disclosed are self-assembling diblock copolymers of the formula (I): 
                         
wherein R 1 -R 4 , n, and m are as described herein, which find use in preparing self-assembled structures and porous membranes. Embodiments of the self-assembled structures contain the diblock copolymer in a cylindrical morphology. Also disclosed is a method of preparing such copolymers.

BACKGROUND OF THE INVENTION

Polymers, in particular block copolymers, which self-assemble intonanostructures have been proposed for use in a number of applicationsincluding filtration membranes, pervaporation membranes, lithography,solid state polymer electrolytes, ion exchange membranes, andbiomaterials. For example, diblock copolymers when dissolved inselective solvents self-assemble into spherical or cylindrical micelles,vesicles and other structures.

However, challenges remain in obtaining well defined nanostructures. Theforegoing indicates that there is an unmet need for block copolymersthat self-assemble under appropriate processing conditions to providewell defined nanostructures.

BRIEF SUMMARY OF THE INVENTION

The invention provides a diblock copolymer of the formula (I):

wherein:

R¹ is a poly(alkyleneoxide) group of the formula, —(CHR—CH₂—O)_(p)—R′,wherein p=2-6, R is H or methyl, and R′ is H, a C₁-C₆ alkyl group, or aC₃-C₁₁ cycloalkyl group;

R² is a C₁-C₂₂ alkyl group or a C₃-C₁₁ cycloalkyl group, each optionallysubstituted with a substituent selected from halo, alkoxy,alkylcarbonyl, alkoxycarbonyl, amido, and nitro;

one of R³ and R⁴ is a C₆-C₁₄ aryl group or a heteroaryl group,optionally substituted with a substituent selected from hydroxy, halo,amino, and nitro, and the other of R³ and R⁴ is a C₁-C₂₂ alkoxy group,optionally substituted with a substituent selected from carboxy, amino,mercapto, alkynyl, alkenyl, halo, azido, and heterocyclyl;

n and m are independently 2 to about 2000.

The invention also provides a process for preparing the diblockcopolymer of formula (I) and porous membranes prepared from the diblockcopolymers.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 depicts the overlaid traces of the Multi-angle Laser LightScattering (MALS) gel permeation chromatograms (GPC) of a homopolymer 1(a precursor to the diblock copolymer) and a diblock copolymer 2 inaccordance with an embodiment of the invention.

FIG. 2 illustrates a porous membrane comprising a diblock copolymer inaccordance with an embodiment of the invention.

FIG. 3 depicts an Atomic Force Micrograph (AFM) phase image of aself-assembled structure prepared in accordance with an embodiment ofthe invention.

FIG. 4 depicts the line profile extracted from FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

In an embodiment, the invention provides a diblock copolymer of theformula (I):

wherein:

R¹ is a poly(alkyleneoxide) group of the formula, —(CHR—CH₂—O)_(p)—R′,wherein p=2-6, R is H or methyl, and R′ is H, a C₁-C₆ alkyl group, or aC₃-C₁ cycloalkyl group;

R² is a C₁-C₂₂ alkyl group or a C₃-C₁₁ cycloalkyl group, each optionallysubstituted with a substituent selected from halo, alkoxy,alkylcarbonyl, alkoxycarbonyl, amido, and nitro;

one of R³ and R⁴ is a C₆-C₁₄ aryl group or a heteroaryl group,optionally substituted with a substituent selected from hydroxy, halo,amino, and nitro, and the other of R³ and R⁴ is a C₁-C₂₂ alkoxy group,optionally substituted with a substituent selected from carboxy, amino,mercapto, alkynyl, alkenyl, halo, azido, and heterocyclyl;

n and m are independently 2 to about 2000.

In accordance with an embodiment, the invention provides a diblockcopolymer of the formula (Ia), where the monomers are exo isomers:

In any of the embodiments above, R is H.

In an embodiment, p is 3-6.

In any of the embodiments, R′ is a C₁-C₆ alkyl group, for example,methyl.

In any of the embodiments, R² is a C₁₀-C₁₈ alkyl group, optionallysubstituted with a substituent selected from halo, alkoxy,alkylcarbonyl, alkoxycarbonyl, amido, and nitro, preferably R² is a C₁₆alkyl group.

In any of the above embodiments, R³ is phenyl.

In any of the above embodiments, R⁴ is a C₁-C₆ alkoxy group.

In an embodiment, R³ is provided by the ROMP catalyst employed for thepolymerization of the monomers.

In an embodiment, R⁴ is a group provided by the vinyl ether compoundemployed for terminating the polymerization.

In accordance with the invention, the term “aryl” refers to a mono, bi,or tricyclic carbocyclic ring system having one, two, or three aromaticrings, for example, phenyl, naphthyl, anthracenyl, or biphenyl. The term“aryl” refers to an unsubstituted or substituted aromatic carbocyclicmoiety, as commonly understood in the art, and includes monocyclic andpolycyclic aromatics such as, for example, phenyl, biphenyl, naphthyl,anthracenyl, pyrenyl, and the like. An aryl moiety generally containsfrom, for example, 6 to 30 carbon atoms, preferably from 6 to 18 carbonatoms, more preferably from 6 to 14 carbon atoms and most preferablyfrom 6 to 10 carbon atoms. It is understood that the term aryl includescarbocyclic moieties that are planar and comprise 4n+2π electrons,according to Hückel's Rule, wherein n=1, 2, or 3.

In accordance with the invention, the term “heteroaryl” refers to acyclic aromatic radical having from five to ten ring atoms of which atleast one atom is O, S, or N, and the remaining atoms are carbon.Examples of heteroaryl radicals include pyridyl, pyrazinyl, pyrimidinyl,pyrrolyl, pyrazolyl, imidazolyl, thiazolyl, oxazolyl, isooxazolyl,thiadiazolyl, oxadiazolyl, thiophenyl, furanyl, quinolinyl, andisoquinolinyl. The term “heteroaryl” as used herein, means a monocyclicheteroaryl or a bicyclic heteroaryl. The monocyclic heteroaryl is afive- or six-membered ring. The five-membered ring consists of twodouble bonds and one sulfur, nitrogen or oxygen atom. Alternatively, thefive-membered ring has two double bonds and one, two, three or fournitrogen atoms and optionally one additional heteroatom selected fromoxygen or sulfur, and the others carbon atoms. The six-membered ringconsists of three double bonds, one, two, three or four nitrogen atoms,and the others carbon atoms. The bicyclic heteroaryl consists of amonocyclic heteroaryl fused to a phenyl, or a monocyclic heteroarylfused to a monocyclic cycloalkyl, or a monocyclic heteroaryl fused to amonocyclic cycloalkenyl, or a monocyclic heteroaryl fused to amonocyclic heteroaryl. The monocyclic and the bicyclic heteroaryl areconnected to the parent molecular moiety through any substitutable atomcontained within the monocyclic or the bicyclic heteroaryl. Themonocyclic and bicyclic heteroaryl groups of the present invention canbe substituted or unsubstituted. In addition, the nitrogen heteroatommay or may not be quaternized, and may or may not be oxidized to theN-oxide. Also, the nitrogen containing rings may or may not beN-protected. Representative examples of monocyclic heteroaryl include,but are not limited to, furanyl, imidazolyl, isoxazolyl, isothiazolyl,oxadiazolyl, oxazolyl, pyridinyl, pyridine-N-oxide, pyridazinyl,pyrimnidinyl, pyrazinyl, pyrazolyl, pyrrolyl, tetrazolyl, thiadiazolyl,thiazolyl, thienyl, triazolyl, and triazinyl. Representative examples ofbicyclic heteroaryl groups include, but not limited to, benzothienyl,benzoxazolyl, benzimidazolyl, benzoxadiazolyl,6,7-dihydro-1,3-benzothiazolyl, imidazo[1,2-a]pyridinyl, indazolyl,1H-indazol-3-yl, indolyl, isoindolyl, isoquinolinyl, naphthyridinyl,pyridoimidazolyl, quinolinyl, quinolin-8-yl, and5,6,7,8-tetrahydroquinolin-5-yl.

The “alkyl” group could be linear or branched. In accordance with anembodiment, the alkyl group is preferably a C₁-C₁₈ alkyl. Examples ofalkyl group include methyl, ethyl, n-propyl, isopropyl, n-butyl,sec-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, n-hexyl,hexadecyl, and the like. This definition also applies wherever “alkyl”occurs such as in hydroxyalkyl, monohalo alkyl, dihalo alkyl, andtrihalo alkyl. The alkyl group can also be further substituted with acycloalkyl group, e.g., a C₃-C₁₁ cycloalkyl group.

In any of the above embodiments, the “cycloalkyl” group can bemonocyclic or bicyclic. Examples of monocyclic cycloalkyl groups includecyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, andcyclooctyl. Examples of bicyclic cycloalkyl groups include those withone common ring carbon atom such as spirooctane, spirononane,spirodecane, and spiroundecane, and those with two common ring carbonatoms such as bicyclooctane, bicyclononane, bicyclodecane, andbicycloundecane. Any of the cycloalkyl groups could be optionallysubstituted with one or more alkyl groups, e.g., C₁-C₆ alkyl groups.

In accordance with an embodiment, the “alkoxy” group is preferably aC₁-C₂₂ alkoxy. Examples of alkoxy group include methoxy, ethoxy,n-propoxy, isopropoxy, n-butoxy, sec-butoxy, isobutoxy, tert-butoxy,n-pentoxy, isopentoxy, n-hexoxy, hexadecyloxy, and the like.

The term “halo” refers to a halogen selected from the group consistingof fluorine, chlorine, bromine, and iodine, preferably chlorine orbromine.

The term “heterocycle” or “heterocyclic” as used herein, means amonocyclic heterocycle or a bicyclic heterocycle. The monocyclicheterocycle is a three-, four-, five-, six- or seven-membered ringcontaining at least one heteroatom independently selected from the groupconsisting of O, N, N(H) and S. The three- or four-membered ringcontains zero or one double bond and a heteroatom selected from thegroup consisting of O, N, N(H) and S. The five-membered ring containszero or one double bond, and one, two or three heteroatoms selected fromthe group consisting of O, N, N(H) and S. The six-membered ring containszero, one or two double bonds and one, two or three heteroatoms selectedfrom the group consisting of O, N, N(H) and S. The seven-membered ringcontains zero, one, two, or three double bonds and one, two or threeheteroatoms selected from the group consisting of O, N, N(H) and S. Themonocyclic heterocycle can be unsubstituted or substituted and isconnected to the parent molecular moiety through any substitutablecarbon atom or any substitutable nitrogen atom contained within themonocyclic heterocycle. Representative examples of monocyclicheterocycle include, but are not limited to, azetidinyl, azepanyl,aziridinyl, diazepanyl, [1,4]diazepan-1-yl, 1,3-dioxanyl,1,3-dioxolanyl, 1,3-dithiolanyl, 1,3-dithianyl, homomorpholinyl,homopiperazinyl, imidazolinyl, imidazolidinyl, isothiazolinyl,isothiazolidinyl, isoxazolinyl, isoxazolidinyl, morpholinyl,oxadiazolinyl, oxadiazolidinyl, oxazohnyl, oxazolidinyl, piperazinyl,piperidinyl, pyranyl, pyrazolinyl, pyrazolidinyl, pyrrolinyl,pyrrolidinyl, tetrahydrofuranyl, tetrahydropyranyl, tetrahydrothienyl,thiadiazolinyl, thiadiazolidinyl, thiazolinyl, thiazolidinyl,thiomorpholinyl, 1,1-dioxidothiomorpholinyl (thiomorpholine sulfone),thiopyranyl, and trithianyl. The bicyclic heterocycle is a monocyclicheterocycle fused to a phenyl group, or a monocyclic heterocycle fusedto a monocyclic cycloalkyl, or a monocyclic heterocycle fused to amonocyclic cycloalkenyl, a monocyclic heterocycle fused to a monocyclicheterocycle, or a monocyclic heterocycle fused to a monocyclicheteroaryl. The bicyclic heterocycle is connected to the parentmolecular moiety through any substitutable carbon atom or anysubstitutable nitrogen atom contained within the bicyclic heterocycleand can be unsubstituted or substituted. Representative examples ofbicyclic heterocycle include, but are not limited to, benzodioxinyl,benzopyranyl, thiochromanyl, 2,3-dihydroindolyl, indolizinyl,pyranopyridinyl, 1,2,3,4-tetrahydroisoquinolinyl,1,2,3,4-tetrahydroquinolinyl, thiopyranopyridinyl,2-oxo-1,3-benzoxazolyl, 3-oxo-benzoxazinyl, 3-azabicyclo[3.2.0]heptyl,3,6-diazabicyclo[3.2.0]heptyl, octahydrocyclopenta[c]pyrrolyl,hexahydro-1H-furo[3,4-c]pyrrolyl, octahydropyrrolo[3,4-c]pyrrolyl,2,3-dihydrobenzofuran-7-yl, 2,3-dihydrobenzofuran-3-yl, and3,4-dihydro-2H-chromen-4-yl. The monocyclic or bicyclic heterocycles asdefined herein may have two of the non-adjacent carbon atoms connectedby a heteroatom selected from N, N(H), O or S, or an alkylene bridge ofbetween one and three additional carbon atoms. Representative examplesof monocyclic or bicyclic heterocycles that contain such connectionbetween two non-adjacent carbon atoms include, but not limited to,2-azabicyclo[2.2.2]octyl, 2-oxa-5-azabicyclo[2.2.2]octyl,2,5-diazabicyclo[2.2.2]octyl, 2-azabicyclo[2.2.1]heptyl,2-oxa-5-azabicyclo[2.2.1]heptyl, 2,5-diazabicyclo[2.2.1]heptyl,2-azabicyclo[2.1.1]hexyl, 5-azabicyclo[2.1.1]hexyl,3-azabicyclo[3.1.1]heptyl, 6-oxa-3-azabicyclo[3.1.1]heptyl,8-azabicyclo[3.2.1]octyl, 3-oxa-8-azabicyclo[3.2.1]octyl,1,4-diazabicyclo[3.2.2]nonyl, 1,4-diazatricyclo[4.3.1.1 3,8]undecyl,3,10-diazabicyclo[4.3.1]decyl, or 8-oxa-3-azabicyclo[3.2.1]octyl,octahydro-1H-4,7-methanoisoindolyl, andoctahydro-1H-4,7-epoxyisoindolyl. The nitrogen heteroatom may or may notbe quaternized, and may or may not be oxidized to the N-oxide. Inaddition, the nitrogen containing heterocyclic rings may or may not beN-protected.

Examples of heterocyclyl groups include pyridyl, piperidinyl,piperazinyl, pyrazinyl, pyrolyl, pyranyl, tetrahydropyranyl,tetrahydrothiopyranyl, pyrrolidinyl, furanyl, tetrahydrofuranyl,thiophenyl, tetrahydrothiophenyl, purinyl, pyrimidinyl, thiazolyl,thiazolidinyl, thiazolinyl, oxazolyl, triazolyl, tetrazolyl, tetrazinyl,benzoxazolyl, morpholinyl, thiophorpholinyl, quinolinyl, andisoquinolinyl.

Five-membered unsaturated heterocyclics with and without benzo: furanyl,thiopheneyl, pyrrolyl, pyrazolyl, pyrazolinyl, imidazolyl, imidazolinyl,dithiazolyl, furazanyl, 1,2,3-triazolyl, tetrazolyl, 1,2,4-triazolyl,oxadiazolyl, thiadiazolyl, isoxazolyl, isoxazolinyl, oxazolyl,oxazolinyl, phospholyl, isothiazolyl, thiazolyl, thiazolinyl,isothiazolyl, isothiazolidinyl, benzofuranyl, benzothiopheneyl, indolyl,benzimidazolyl, benzoxazolinyl, and benzothiazolinyl.

Whenever a range of the number of atoms in a structure is indicated(e.g., a C₁₋₂₂, a C₁₋₁₂, C₁₋₈, C₁₋₆, or C₁₋₄ alkyl, alkoxy, etc.), it isspecifically contemplated that any sub-range or individual number ofcarbon atoms falling within the indicated range also can be used. Thus,for instance, the recitation of a range of 1-22 carbon atoms (e.g.,C₁-C₂₂), 1-20 carbon atoms (e.g., C₁-C₂₀), 1-18 carbon atoms (e.g.,C₁-C₂₀), 1-16 carbon atoms (e.g., C₁-C₁₆), 1-14 carbon atoms (e.g.,C₁-C₁₄), 1-12 carbon atoms (e.g., C₁-C₁₂), 1-10 carbon atoms (e.g.,C₁-C₁₀), 1-8 carbon atoms (e.g., C₁-C₈), 1-6 carbon atoms (e.g., C₁-C₆),1-4 carbon atoms (e.g., C₁-C₄), 1-3 carbon atoms (e.g., C₁-C₃), or 2-8carbon atoms (e.g., C₂-C₈) as used with respect to any chemical group(e.g., alkyl, alkoxy, alkylamino, etc.) referenced herein encompassesand specifically describes 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,14, 15, 16, 17, 18, 19, 20, 21, or 22 carbon atoms, as appropriate, aswell as any sub-range thereof, e.g., 1-2 carbon atoms, 1-3 carbon atoms,1-4 carbon atoms, 1-5 carbon atoms, 1-6 carbon atoms, 1-7 carbon atoms,1-8 carbon atoms, 1-9 carbon atoms, 1-10 carbon atoms, 1-11 carbonatoms, 1-12 carbon atoms, 1-13 carbon atoms, 1-14 carbon atoms, 1-15carbon atoms, 1-16 carbon atoms, 1-17 carbon atoms, 1-18 carbon atoms,1-19 carbon atoms, 1-20 carbon atoms, 1-21 carbon atoms, and 1-22 carbonatoms, and anything in between such as 2-3 carbon atoms, 2-4 carbonatoms, 2-5 carbon atoms, 2-6 carbon atoms, 2-7 carbon atoms, 2-8 carbonatoms, 2-9 carbon atoms, 2-10 carbon atoms, 2-11 carbon atoms, 2-12carbon atoms, 2-12 carbon atoms, 2-13 carbon atoms, 2-14 carbon atoms,2-15 carbon atoms, 2-16 carbon atoms, 2-17 carbon atoms, 2-18 carbonatoms, 2-19 carbon atoms, 2-20 carbon atoms, 2-21 carbon atoms, and 2-22carbon atoms, 3-4 carbon atoms, 3-5 carbon atoms, 3-6 carbon atoms, 3-7carbon atoms, 3-8 carbon atoms, 3-9 carbon atoms, 3-10 carbon atoms,3-11 carbon atoms, 3-12 carbon atoms, 3-13 carbon atoms, 3-14 carbonatoms, 3-15 carbon atoms, 3-16 carbon atoms, 3-17 carbon atoms, 3-18carbon atoms, 3-19 carbon atoms, 3-20 carbon atoms, 3-21 carbon atoms,and 3-22 carbon atoms, and 4-5 carbon atoms, 4-6 carbon atoms, 4-7carbon atoms, 4-8 carbon atoms, 4-9 carbon atoms, 4-10 carbon atoms,4-11 carbon atoms, 4-12 carbon atoms, 4-13 carbon atoms, 4-14 carbonatoms, 4-15 carbon atoms, 4-16 carbon atoms, 4-17 carbon atoms, 4-18carbon atoms, 4-19 carbon atoms, 4-20 carbon atoms, 4-21 carbon atoms,4-22 carbon atoms, etc., as appropriate.

In the above embodiments, “n” and “m” represent the average degree ofpolymerization of the respective monomers.

In accordance with embodiments of the invention, n is about 10 to about1000, about 10 to about 500, about 10 to about 250, about 20 to about1000, about 20 to about 500, about 20 to about 250, about 30 to about1000, about 30 to about 500, about 30 to about 250, about 40 to about1000, about 40 to about 500, about 40 to about 250, about 50 to about1000, about 50 to about 500, about 50 to about 250, about 60 to about1000, about 60 to about 500, or about 60 to about 250.

In any of the above embodiments, m is about 50 to about 2000, about 50to about 1500, about 50 to about 1000, about 100 to about 2000, about100 to about 1500, about 100 to about 1000, about 150 to about 2000,about 150 to about 1500, about 150 to about 1000, about 200 to about2000, about 200 to about 1500, or about 200 to about 1000.

In any of the above embodiments of the diblock copolymer, n is typicallyabout 30 to about 350, preferably about 70 to about 200, and morepreferably about 100 to about 150.

In any of the above embodiments, m is typically about 75 to about 900,preferably about 180 about 500, and more preferably about 250 to about400.

The diblock copolymer can have any suitable total molecular weight, forexample, a number average molecular weight (M_(n)) of from about 35 kDato about 450 kDa; in certain embodiments, the diblock copolymer has anM_(n) of from about 75 kDa to about 300 kDa; in certain otherembodiments, the diblock copolymer has an M_(n) of about 250 kDa. In anembodiment, the diblock copolymer has an M_(n) of 129 kDa.

The double bonds in the diblock copolymer can have any suitableorientation, cis, trans, and they can be distributed in a random manner.

The diblock copolymer may self-assemble into any suitable morphology,for example, but not limited to, spherical or body centered cubicmorphology, cylindrical morphology, lamellar morphology, or doublegyroid morphology. The type of nanostructure into which the copolymersself-assemble would depend, among others, on the volume fraction of thetwo blocks in the block copolymer as well as the nature of the solventsystem.

For example, at a polymer volume fraction ratio range (f_(A):f_(B)) ofthe two monomers of 37-50:63-50, formation of a lamellar morphologyinvolving a stack of layers of equivalent domain size is favored, at avolume fraction ratio range of 15-70:85-30, formation of a cylindricalmorphology where the minor polymer component forms cylinders in a matrixof major polymer block component is favored, and at a volume fractionratio range of 7-15:83-85, formation of spherical morphology or bodycentered cubic (bcc) morphology where the minor polymer component formsspheres in a matrix of the major polymer block component is favored. Ata volume fraction ratio range of 33-37:67-33, formation of a doublegyroid morphology is favored.

Cylindrical morphology includes a phase domain morphology havingdiscrete tubular or cylindrical shapes. The tubular or cylindricalshapes may be hexagonally packed on a hexagonal lattice. In embodiments,the cylindrical domain size is from about 5 nm to about 100 nm.

Lamellar morphology includes a phase domain morphology having layers ofalternating compositions that are generally oriented parallel withrespect to one another. In embodiments, the lamellar domain size is fromabout 5 nm to about 100 nm.

The double gyroid morphology comprises two interpenetrating continuousnetwork. In embodiments, the double gyroid domain size is from about 5nm to about 100 nm.

Spherical morphology or bcc morphology refers to a phase domainmorphology having spherical domains of one block arranged on a bodycentered cubic lattice in a matrix of the second block. In embodiments,the spherical morphology domain size is from about 5 nm to about 100 nm.

In an embodiment, the polymerized second monomer (bearing R²) and thepolymerized first monomer (bearing R¹) are present in the diblockcopolymer in any suitable volume fraction. For example, the % volumefraction of the first monomer to that of the second monomer can be inthe range of from about 15:about 85 to about 30:about 70, preferably inthe range of from about 19:about 81 to about 25:about 75, and morepreferably about 20:about 80. In an embodiment, the volume fraction ofthe second monomer is about 74% of the total polymer.

In an embodiment, the volume fraction of the second monomer to that ofthe first monomer is about 2.8:1, which favors the formation ofcylindrical morphology when the block copolymer self-assembles. The massfraction of the second monomer to that of the first monomer is about2.2:1.

In a specific embodiment, the diblock copolymer of formula (I) has thefollowing structure, in particular, wherein n is 100 and m is 180:

In an embodiment, the diblock copolymer of formula (I) has the followingstructure where the monomers are in the exo configuration, inparticular, wherein n is 100 and m is 180:

The present invention further provides a method of preparing diblockcopolymers of formula (I) described above, comprising:

(i) polymerizing one of the two monomers of the formulas:

with a ring opening metathesis polymerization (ROMP) catalyst to obtaina ring-opened polymer having a living chain end;

(ii) polymerizing the other of the two monomers on the living end of thering-opened polymer obtained in (i) to obtain a diblock copolymer havinga living end; and

(iii) terminating the living end of the diblock copolymer obtained in(ii) with an optionally substituted alkyl vinyl ether.

The alkyl group of the alkyl vinyl ether could be optionally substitutedwith a substituent, for example, a substituent selected from hydroxy,halo, amino, and nitro.

In an embodiment of the above method, the monomer that is firstpolymerized is of the formula:

After the polymerization of the above monomer, the second monomer thatis polymerized thereon is a monomer of the formula:

The first monomer and the second monomer can be an exo or endostereochemical configuration. In an embodiment, the first and secondmonomers are of the exo configuration, e.g., a monomer having the exoisomer at 98% or higher.

In the first and second monomers, R¹ and R² are the same as describedabove for the diblock copolymer of formula (I). In an embodiment, thefirst and second monomers are (oxa)norbornene (di)carboxylic imidederived monomers.

The monomers can be prepared by any suitable method, for example,starting from maleimide and furan via a Diels-Alder reaction,illustrated below:

The first monomer can be synthesized via Mitsunobu Coupling reaction, asillustrated below:

Alternatively, the first monomer can be synthesized by the reaction ofN-triethyleneglycol monomethylethermaleimide with furan via aDiels-Alder reaction.

The second monomer can be synthesized via Mitsunobu Coupling, asillustrated below.

Alternatively, the second monomer can be synthesized by the reaction ofexo-7-oxanorbornene-5,6-dicarboxyanhydride with hexadecylamine orN-hexadecyl-maleimide reaction with furan via Diels Alder reaction.

The polymerization of the monomers is carried out by ring-opening olefinmetathesis polymerization (ROMP), in which a cyclic olefin monomer ispolymerized or copolymerized by ring-opening of the cyclic olefinmonomer. Typically a transition metal catalyst containing a carbeneligand mediates the metathesis reaction.

Any suitable ROMP catalyst can be used, for example, Grubbs' first,second, and third generation catalysts, Umicore, Hoveyda-Grubbs,Schrock, and Schrock-Hoveyda catalysts can be employed. Examples of suchcatalysts include the following:

In an embodiment, Grubbs' third generation catalysts are particularlysuitable due to their advantages such as stability in air, tolerance tomultiple functional groups, and/or fast polymerization initiation andpropagation rates. In addition, with the Grubbs' third generationcatalysts, the end groups can be engineered to accommodate anycompatible groups, and the catalyst can be recycled readily. An exampleof such a catalyst is:

The above third generation Grubbs catalyst may be obtained commerciallyor prepared from a Grubbs second generation catalyst (G2) as follows:

The first monomer and the second monomer are polymerized sequentially toobtain the diblock copolymer. In accordance with the invention, any oneof the two monomers can be polymerized. For example, the first monomercan be polymerized first, followed by the second monomer. Alternatively,the second monomer can be polymerized first, followed by the firstmonomer.

Typically, the monomers have a chemical purity of at least 95%,preferably 99% or greater, and more preferably 99.9% or greater. It ispreferred that the monomers are free of impurities that will interferewith the polymerization, e.g., impurities that will affect the ROMPcatalyst. Examples of such impurities include amines, thiols, acids,phosphines, and N-substituted maleimides.

The polymerization of the monomers is conducted in a suitable solvent,for example, solvents generally used for conducting ROMPpolymerizations. Examples of suitable solvents include aromatichydrocarbons such as benzene, toluene, and xylene, aliphatichydrocarbons such as n-pentane, hexane, and heptane, alicylichydrocarbons such as cyclohexane, and halogenated hydrocarbons such asdichloromethane, dichloroethane, dichloroethylene, tetrachloroethane,chlorobenzene, dichlorobenzene, and trichlorobenzene, as well asmixtures thereof.

When polymerization is carried out in the organic solvent, the monomerconcentration can be in the range of 1 to 50 wt %, preferably 2 to 45 wt%, and more preferably 3 to 40 wt %.

The polymerization can be carried out at any suitable temperature, forexample, from −20 to +100° C., preferably 10 to 80° C.

The polymerization can be carried out for any time suitable to obtainthe appropriate chain length of each of the blocks, which can be fromabout 1 minute to 100 hours.

The amount of catalyst can be chosen in any suitable amount. Forexample, the molar ratio of the catalyst to the monomer can be about1:10 to about 1:1000, preferably about 1:50 to about 1:500, and morepreferably about 1:100 to about 1:200. For example, the molar ratio ofthe catalyst to the monomer could be 1:n and 1:m, where n and m are theaverage degrees of polymerization.

After the polymerization of the two monomers, the chain end of thediblock copolymer is terminated by adding an optionally substitutedalkyl vinyl ether to the polymerization mixture.

The diblock copolymer can be isolated by a suitable technique such asprecipitation with a nonsolvent.

The homopolymer formed during the preparation of the diblock copolymerand the diblock copolymer of the invention can be characterized for itsmolecular weight and molecular weight distribution by any knowntechniques. For example, a MALS-GPC technique can be employed. Thetechnique uses a mobile phase to elute, via a high pressure pump, apolymer solution through a bank of columns packed with a stationaryphase. The stationary phase separates the polymer sample according tothe chain size followed by detecting the polymer by three differentdetectors. A series of detectors can be employed, e.g., an Ultravioletdetector (UV-detector), followed by a multi-angle laser light scatteringdetector (MALS-detector), which in turn, is followed by a refractiveindex detector (RI-detector) in a row. The UV-detector measures thepolymer light absorption at 254 nm wavelength; the MALS-detectormeasures the scattered light from polymer chains relative to mobilephase.

The diblock copolymers of the invention are highly monodisperse. Forexample, the copolymers have an Mw/Mn of 1.01 to 1.2, preferably 1.05 to1.10.

The present invention further provides a porous membrane comprising adiblock copolymer described above. The diblock copolymer can bedissolved in a suitable solvent system. For example, the solvent systemincludes a solvent or a mixture of solvents selected fromdichloromethane, 1-chloropentane, chloroform, 1,1-dichloroethane,N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA),N-methylpyrrolidone (NMP), dimethylsulfoxide (DMSO), tetrahydrofuran(THF), 1,3-dioxane, and 1,4-dioxane.

The polymer solution is cast as a thin film on a suitable substrate byany suitable method, for example, spin coating, hybrid casting, or spraycoating. For example, in hybrid casting, the solvent is allowed toevaporate from the thin film so that the diblock copolymer undergoesself-assembly into an ordered nanostructure. The coating which containsnanostructure is allowed to undergo phase inversion by immersing it in anonsolvent such as isopropanol, pentane, or hexane, or a mixturecontaining isopropanol, DMSO, and/or water. The cross-section of amembrane according to an embodiment of the invention is illustrated inFIG. 2 and is characterized by a thin nanoporous layer at the top wherethe polymer assumes a cylindrical morphology, which is supported by aporous polymer layer of random morphology.

Alternatively, the polymer solution can be spin coated on a substratesuch as glass plate or silicon wafer. The wet film is annealed in asolvent vapor, e.g., dichloromethane vapor, for a period of about 1 hrto about 3 days or more in order for the polymer to self-assemble intoan ordered structure. FIG. 3 depicts an AFM phase image of aself-assembled structure prepared in accordance with an embodiment ofthe invention. FIG. 4 depicts the line profile extracted from FIG. 3,showing periodicity.

A porous membrane can be prepared from the self-assembled structure viaconfined swelling leading to the generation of pores. Confined swellingis effected by an annealing step, which could be carried out either byexposing the self-assembled structure to a solvent vapor or by soakingin a liquid solvent.

A porous structure can be generated from the self-assembled structure,particularly one with cylindrical morphology, via a confined swellingstep, which is carried by annealing. The annealing step could be done ineither a solvent vapor or soaking in liquid solvent. The solvent shouldbe a good solvent for the minor volume fraction block that forms thecylinder core and non-solvent for the major volume block forming thematrix. While not intending to be held to any theory or mechanism, it isbelieved that, as the self-assembled structure is annealed the cylindercore becomes swollen by the solvent, leading to an increase of thecylinder volume. As the cylinder cores spread outside the matrixsurface, the spreading forces the cylinders to create pores. The matrixthickness also increases.

Examples of solvents that can be used for the annealing includetetrahydrofuran (THF), butyacetate, ethylactate, methylethylketone, andacetone. The solvent or mixture of solvents can be at any suitabletemperature, for example, from ambient temperature, for example, 20° C.to 25° C., to elevated temperatures, such as up to 40° C., 50° C., 60°C., 70° C., 80° C., or 90° C.

In accordance with an embodiment of the invention, the porous membraneis a nanoporous membrane, for example, a membrane having pores ofdiameter between 1 nm and 100 nm.

Membranes according to embodiments of the invention can be used in avariety of applications, including, for example, diagnostic applications(including, for example, sample preparation and/or diagnostic lateralflow devices), ink jet applications, filtering fluids for thepharmaceutical industry, filtering fluids for medical applications(including for home and/or for patient use, e.g., intravenousapplications, also including, for example, filtering biological fluidssuch as blood (e.g., to remove leukocytes)), filtering fluids for theelectronics industry (e.g., filtering photoresist fluids in themicroelectronics industry), filtering fluids for the food and beverageindustry, clarification, filtering antibody- and/or protein-containingfluids, filtering nucleic acid-containing fluids, cell detection(including in situ), cell harvesting, and/or filtering cell culturefluids. Alternatively, or additionally, membranes according toembodiments of the invention can be used to filter air and/or gas and/orcan be used for venting applications (e.g., allowing air and/or gas, butnot liquid, to pass therethrough). Membranes according to embodiments ofthe inventions can be used in a variety of devices, including surgicaldevices and products, such as, for example, ophthalmic surgicalproducts.

In accordance with embodiments of the invention, the membrane can have avariety of configurations, including planar, flat sheet, pleated,tubular, spiral, and hollow fiber.

Membranes according to embodiments of the invention are typicallydisposed in a housing comprising at least one inlet and at least oneoutlet and defining at least one fluid flow path between the inlet andthe outlet, wherein at least one inventive membrane or a filterincluding at least one inventive membrane is across the fluid flow path,to provide a filter device or filter module. In an embodiment, a filterdevice is provided comprising a housing comprising an inlet and a firstoutlet, and defining a first fluid flow path between the inlet and thefirst outlet; and at least one inventive membrane or a filter comprisingat least one inventive membrane, the inventive membrane or filtercomprising at least one inventive membrane being disposed in the housingacross the first fluid flow path.

Preferably, for crossflow applications, at least one inventive membraneor filter comprising at least one inventive membrane is disposed in ahousing comprising at least one inlet and at least two outlets anddefining at least a first fluid flow path between the inlet and thefirst outlet, and a second fluid flow path between the inlet and thesecond outlet, wherein the inventive membrane or filter comprising atleast one inventive membrane is across the use the first fluid flowpath, to provide a filter device or filter module. In an illustrativeembodiment, the filter device comprises a crossflow filter module, thehousing comprising an inlet, a first outlet comprising a concentrateoutlet, and a second outlet comprising a permeate outlet, and defining afirst fluid flow path between the inlet and the first outlet, and asecond fluid flow path between the inlet and the second outlet, whereinat least one inventive membrane or filter comprising at least oneinventive membrane is disposed across the first fluid flow path.

The filter device or module may be sterilizable. Any housing of suitableshape and providing an inlet and one or more outlets may be employed.

The housing can be fabricated from any suitable rigid imperviousmaterial, including any impervious thermoplastic material, which iscompatible with the fluid being processed. For example, the housing canbe fabricated from a metal, such as stainless steel, or from a polymer,e.g., transparent or translucent polymer, such as an acrylic,polypropylene, polystyrene, or a polycarbonate resin.

The following examples further illustrate the invention but, of course,should not be construed as in any way limiting its scope.

EXAMPLE 1

This example provides the materials used in the preparation of themonomers and polymers.

Maleimide, furan, diisopropylazodicarboxylate (DIAD), triphenylphosphine(Ph₃P), 1-haxadecanol, tetrahydrofuran (THF), ethyl acetate,N-phenylmaleimide, acetonitrile, methanol, Grubbs second generationcatalyst, 3-bromopyridine, and pentane were obtained from Sigma-AldrichCo. and used without further treatment. Dichloropentane, also obtainedfrom Sigma-Aldrich Co., was treated with basic alumina before use.

EXAMPLE 2

This example illustrates the preparation ofexo-7-oxanorbornene-5,6-dicarboxyimide (C1), an intermediate in thepreparation of the first and second monomers in accordance with anembodiment of the invention.

In a clean 500 mL round bottom flask (RBF) equipped with a magneticstirring bar, furan (21.0 g, 309 mmol) was added to a solution ofmaleimide (25 g, 258 mmol) in 250 mL of ethyl acetate. The mixture washeated at 90° C. for 30 h. C1 was obtained as white precipitate fromsolution upon washing with ether (100 mL, 3×) and filtration. The whitesolid was dried under vacuum at room temperature for 24 h. C1 wasobtained as a pure exo-isomer in yield of 29 g, 68%. ¹H-NMR (300 MHz,CDCl₃): δ (ppm) 8.09 (s, 1H), 6.53 (s, 2H), 5.32 (s, 2H), 2.89 (s, 2H).

EXAMPLE 3

This example illustrates the preparation ofdichloro[1,3-bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene](benzylidene)bis(3-bromopyridine)ruthenium(II)(G3) catalyst.

The second generation Grubbs catalyst illustrated above (G2) (1.0 g,1.18 mmol) was mixed with 3-bromopyridine (1.14 mL, 11.8 mmol) in 50 mLflask. Upon stirring at room temperature for 5 min, the red mixtureturned into bright green. Pentane (40 mL) was added with stirring for 15minutes and green solid was obtained. The mixture was cooled in thefreezer for 24 h and filtered under vacuum. The resulting G3 catalyst, agreen solid, was washed with cold pentane and dried under vacuum at roomtemperature to give a yield of 0.9 g, 88% yield.

EXAMPLE 4

This example illustrates the preparation of monomerexo-7-oxanorbornene-N-triethyleneglycol-monomethylether-5,6-dicarboxyimidein accordance with an embodiment of the invention.

A 1 L round-bottom flask was charged withexo-7-oxanorbornene-5,6-dicarboxyimide (82.6 g; 0.5 mol),triethyleneglycol monomethyl ether (70.4 mL; 0.45 mol) andtriphenylphosphine (144.3 g; 0.55 mol). The contents were vigorouslystirred with anhydrous tetrahydrofuran (650 mL) until all the solidsdissolved. The mixture was cooled in an ice-bath, followed by thedrop-wise addition of diethyl azodicarboxylate (87 mL; 0.55 mol) dilutedwith anhydrous tetrahydrofuran (50 mL), while maintaining vigorousstirring and ice cooling. The reaction was allowed to slowly warm up toambient temperature and stirring continued for 24-48 h. Tetrahydrofuranwas removed by rotary evaporation and the concentrate was diluted withdiethyl ether (1 L) and the resulting slurry was stirred at ambienttemperature for 4 h. The insoluble solids were filtered off, washed withdiethyl ether (2×150 mL), and the filtrate and the washes were combinedand concentrated by rotary evaporation. The resulting residue wasdiluted with distilled water (750 mL) with vigorous stirring. Theprecipitate was filtered off, washed with water (2×75 mL) and thefiltrate and the washes were combined and extracted with diethyl ether(4×200 mL). The aqueous layer was saturated by adding solid NaClfollowed by extraction with dichloromethane (5×200 mL). Ethereal anddichloromethane extracts were then analyzed by TLC and fractions deemedsufficiently pure were pooled, dried with anhydrous magnesium sulfate,filtered and concentrated to constant weight. The obtained yellowishviscous liquid was characterized by NMR analysis to be sufficiently purefor conducting polymerizations. The product yield was 81.4 g (60%).¹H-NMR (300 MHz, CDCl₃): 6.51 (s, 2H), 5.26 (s, 2H), 3.65-3.72 (m, 2H),3.55-3.62 (m, 8H), 3.51-3.54 (m, 2H), 3.37 (s, 3H), 2.87 (s, 2H).

EXAMPLE 5

This example illustrates the preparation of monomerexo-7-oxanorbornene-N-hexadecyl-5,6-dicarboxyimide in accordance with anembodiment of the invention.

In a clean 500 mL RBF equipped with magnetic stirring bar, a mixture ofexo-7-oxanorbornene-5,6-dicarboxyimide (C1) (10 g, 61 mmol), Ph₃P (23.84g, 91 mmol), and 1-hexadecanol (17.6 g, 72.7 mmol) was dissolved inanhydrous THF (130 mL) under a stream of dry nitrogen gas. The solutionwas cooled in ice bath. DIAD (22.1 g, 109.3 mmol) was added fromdropping funnel drop-wise to the cooled solution. The reaction mixturewas allowed to warm up to room temperature and stirred for 24 h. THF wasremoved by rotary evaporation till dryness to obtain a white solid. Themonomer was obtained from the crude as white solid upon crystallizationfrom methanol (2×) and drying at room temperature under vacuum for 24 h(yield of 18.6 g, 80%). ¹H-NMR (300 MHz, CDCl₃): δ (ppm) 6.5 (s, 2H),5.26 (s, 2H), 5.32 (s, 2H), 3.45 (t, 2H), 2.82 (s, 2H), 1.56-1.38 (m,2H), 1.28-1.1 (m, 24H), 0.88 (t, 3H).

EXAMPLE 6

This example illustrates the preparation of a diblock copolymer inaccordance with an embodiment of the invention.

The Grubbs 3^(rd) generation (G3) catalyst (57 mg, 0.064 mmol) wasweighed in a 40 mL vial equipped with a fluoropolymer resin-siliconesepta open-top cap. The G3 was dissolved in argon-degassed DCM (30 mL)and transferred via a cannula to a clean 1 L RBF equipped with astirring bar. A solution of the monomer from Example 4 (2.0 g, 6.42mmol) in DCM (5 mL) was degassed with argon and transferred into the G3solution and stirred for 80 minutes. An aliquot of 1-2 mL of thehomopolymer formed was taken after 80 minutes for molecular weightcharacterization. A solution of the monomer from Example 5 (6.25 g, 16.1mmol) in DCM (320 mL) was degassed with argon and transferred into thegrowing homopolymer solution and was stirred for another 65 minutes.Ethylvinylether (2 mL) was added to the yellow solution of the diblockcopolymer to terminate the reaction and allowed to stir for another 20min. The polymer was precipitated in MeOH (2 L, 2×) to recover the purepolymer as a white solid. The polymer was filtered and dried undervacuum at room temperature. ¹H-NMR (300 MHz, CDCl₃): δ (ppm) 6.0 (sbroad, 2H,), 5.7 (s broad, 2H), 5.2-4.8 (s broad, 2H), 4.6-4.3 (s broad,2H), 3.9-3.1 (broad m, 17H), 1.8-1.4 (broad m, 2H), 1.36-0.9 (s broad,28H) 0.88 (t, 3H).

EXAMPLE 7

This example illustrates a method to characterize the diblock copolymerof the present invention involving the Multi-angle Laser LightScattering and gel permeation chromatography (GPC).

The homopolymer and diblock copolymer obtained in Example 6 wascharacterized for their molecular weight and molecular weightdistribution properties by the MALS-GPC technique under the followingconditions:

Mobile phase: Dichloromethane (DCM).

Mobile phase temperature: 30° C.

UV wavelength: 245 nm.

Columns used: three PSS SVD Lux analytical columns(Styrene-divinylbenzene copolymer network), columns have stationaryphase beads of 5 micrometers and has the pore sizes of 1000 A, 100,000A, and 1,000,000 A, and guard columns.

Flow rate: 1 mL/min.

GPC system: waters HPLC alliance e2695 system with UV and RI detectors

MALS system: The DAWN HELEOS 8 system with 8 detectors operating a laserat 664.5 nm.

The chromatograms are depicted in FIG. 1. The diblock copolymer 2 elutedearlier than homopolymer 1 since it has a higher molecular weight.

EXAMPLE 8

This example illustrates a method of preparing a self-assembledstructure from the diblock copolymer in accordance with an embodiment ofthe invention.

A 1.0% mass per volume solution of the diblock copolymer from Example 6was prepared in a mixture of N,N-dimethylformamide (DMF) andtetrahydrofuran (THF) of 70/30 volume % composition. The solution wasstirred at room temperature for 3 days before use.

A thin film of each of the above polymer solution was spin coated on aglass substrate for 90 sec at a spinning rate of 2000 rpm. The thin filmwas annealed in a vapor of dichloromethane for 3 days. The resultingthin film was washed and dried to obtain a self-assembled structure.

FIG. 3 depicts the AFM phase image of the surface of the self-assembledstructure.

All references, including publications, patent applications, andpatents, cited herein are hereby incorporated by reference to the sameextent as if each reference were individually and specifically indicatedto be incorporated by reference and were set forth in its entiretyherein.

The use of the terms “a” and “an” and “the” and “at least one” andsimilar referents in the context of describing the invention (especiallyin the context of the following claims) are to be construed to coverboth the singular and the plural, unless otherwise indicated herein orclearly contradicted by context. The use of the term “at least one”followed by a list of one or more items (for example, “at least one of Aand B”) is to be construed to mean one item selected from the listeditems (A or B) or any combination of two or more of the listed items (Aand B), unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted. Recitation of ranges of valuesherein are merely intended to serve as a shorthand method of referringindividually to each separate value falling within the range, unlessotherwise indicated herein, and each separate value is incorporated intothe specification as if it were individually recited herein. All methodsdescribed herein can be performed in any suitable order unless otherwiseindicated herein or otherwise clearly contradicted by context. The useof any and all examples, or exemplary language (e.g., “such as”)provided herein, is intended merely to better illuminate the inventionand does not pose a limitation on the scope of the invention unlessotherwise claimed. No language in the specification should be construedas indicating any non-claimed element as essential to the practice ofthe invention.

Preferred embodiments of this invention are described herein, includingthe best mode known to the inventors for carrying out the invention.Variations of those preferred embodiments may become apparent to thoseof ordinary skill in the art upon reading the foregoing description. Theinventors expect skilled artisans to employ such variations asappropriate, and the inventors intend for the invention to be practicedotherwise than as specifically described herein. Accordingly, thisinvention includes all modifications and equivalents of the subjectmatter recited in the claims appended hereto as permitted by applicablelaw. Moreover, any combination of the above-described elements in allpossible variations thereof is encompassed by the invention unlessotherwise indicated herein or otherwise clearly contradicted by context.

The invention claimed is:
 1. A diblock copolymer of the formula (I):

wherein: R¹ is a poly(alkyleneoxide) group of the formula, —(CHR—CH₂—O)_(p)—R′, wherein p=2-6, R is H or methyl, and R′ is H, a C₁-C₆ alkyl group, or a C₃-C₁₁ cycloalkyl group; R² is a C₁-C₂₂ alkyl group or a C₃-C₁₁ cycloalkyl group, each optionally substituted with a substituent selected from halo, alkoxy, alkylcarbonyl, alkoxycarbonyl, amido, and nitro; one of R³ and R⁴ is a C₆-C₁₄ aryl group or a heteroaryl group, optionally substituted with a substituent selected from hydroxy, halo, amino, and nitro, and the other of R³ and R⁴ is a C₁-C₂₂ alkoxy group, optionally substituted with a substituent selected from carboxy, amino, mercapto, alkynyl, alkenyl, halo, azido, and heterocyclyl; and n and m are independently 2 to about 2000; wherein the volume fraction of the monomer bearing R² to that of the monomer bearing R¹ in the block copolymer is about 2.8:1.
 2. The diblock copolymer of claim 1, wherein R is H.
 3. The diblock copolymer of claim 1, wherein p is 3-6.
 4. The diblock copolymer of claim 1, wherein R′ is a C₁-C₆ alkyl group.
 5. The diblock copolymer of claim 1, wherein R′ is methyl.
 6. The diblock copolymer of claim 1, wherein R² is a C₁₀-C₁₈ alkyl group, optionally substituted with a substituent selected from halo, alkoxy, alkylcarbonyl, alkoxycarbonyl, amido, and nitro.
 7. The diblock copolymer of claim 1, wherein R² is a C₁₆ alkyl group.
 8. The diblock copolymer of claim 1, wherein R³ is phenyl.
 9. The diblock copolymer of claim 1, wherein R⁴ is a C₁-C₆ alkoxy group.
 10. The diblock copolymer of claim 1, wherein n is about 30 to about 350 and m is about 75 to about
 900. 11. The diblock copolymer of claim 1, wherein n is about 70 to about
 200. 12. The diblock copolymer of claim 1, wherein m is about 180 to about
 500. 13. The diblock copolymer of claim 1, which has the following structure:


14. A method of preparing a diblock copolymer of claim 1, comprising: (i) polymerizing one of the two monomers of the formulas:

with a ring opening metathesis polymerization (ROMP) catalyst to obtain a ring-opened polymer having a living chain end; (ii) polymerizing the other of the two monomers on the living end of the ring-opened polymer obtained in (i) to obtain a diblock copolymer having a living end; and (iii) terminating the living end of the diblock copolymer obtained in (ii) with an optionally substituted alkyl vinyl ether.
 15. The method of claim 14, wherein the ROMP catalyst is of the formula:


16. A self-assembled structure comprising a diblock copolymer of claim
 1. 17. A porous membrane prepared from the self-assembled structure of claim
 16. 